Mechanical combination locks such as those found on safes, vaults, cabinets and other high security enclosures are well known and subject to a number of attacks, such as by drilling, manipulation, and operation by dialer controlled by a computer.
Recently an electronic combination lock for such enclosures has been invented which provides the opportunity to greatly increase the level of security afforded by the lock, while at the same time overcomes many of the shortcomings of the prior art mechanical locks.
A dial type combination lock relies on the rotation of a dial to positions represented by numbers on the dial to rotate mechanical elements within the lock, such that the wheels of the mechanism align to allow a bar to drop into the wheels and retract the lock bar or bolt, allowing the enclosure to be opened.
The electronic combination lock does not have the equivalent mechanical elements and, therefore, can not be attacked in the same manner. For example, the mechanical lock may be drilled to permit the insertion of an optical device into the lock mechanism to observe the positions of the wheels and thus their alignment which permits the opening of the enclosure without the knowledge of the combination.
The electronic lock cannot be drilled for a similar purpose since the electronic lock mechanism will not reveal the position of any element which would be helpful for the attacker to observe and which would give the attacker any information as to the steps need to unlock the device.
The mechanical lock has a fixed position of internal elements relative to the dial and thus may be observed with the movements of the dial repeated by the attacker, at a later time.
The electronic lock does not have a fixed dial to number position relation and thus observation of the movement of the dial is much more difficult if not impossible.
Dialers exist which may be attached to the knob of a dial on a combination lock and which dial combinations under the control of a computer. As each combination fails, the computer then continues to dial other combinations to eventually unlock the lock.
With a combination lock of the mechanical type and sufficient time, a dialer is particularly effective.
The electronic combination locks are dependent upon electronic pulses being generated to indicate to the electronic controls, that the dial is being rotated and in which direction. The pulses may be generated by conventional pulse generation means when a voltage supply is provided to power the pulse generator.
Alternatively, pulses may be generated by the operation of the lock and the the voltage pulses provide a power source for the operation of the lock.
This type of power source eliminates the need for a separate power source for the system, such as a battery or other external voltage supply.
With the control of the device by a series of voltage pulses, the use of the pulses may be used to further control functions of the lock.